The 7.5-hour transit runs from 7:12 a.m. EDT, when Mercury will "start to make a tiny dent in the sun's disk," and until 2:42 p.m. It will be visible in its entirety across the U.S. East Coast, as well as in South America, western Europe and western Africa, according to NASA. Those located in Western U.S. states will be able to view it after sunrise.

It won't be visible to the naked eye. If you don't have your own gear, don't worry. NASA will be streaming the transit live on NASA TV and its Facebook page. You can also watch it live in the video above, courtesy of the robotic telescope company Slooh.

"Astronomers get excited when any two things come close to each other in the heavens," Louis Mayo, program manager at NASA’s Goddard Space Flight Center, said in a statement. "This is a big deal for us."

NASASkywatchers in Western Europe, South America and eastern North America will be able to see the entirety of the transit. The entire 7.5-hour path across the sun will be visible across the Eastern U.S. -- with magnification and proper solar filters -- while those in the West can observe the transit in progress at sunrise.

Mercury transits the sun roughly 13 or 14 times per century. The last one occurred in 2006, with the next two not until Nov. 11, 2019, and Nov. 13, 2032.

For those observing Monday's event with their own telescope, NASA offers these important safety tips: "Use only a commercially available safe solar filter covering the sky-end of a telescope or both sky-ends of a pair of high power binoculars to observe the transit. Sunglasses and crossed polarizers are not dark enough to save your retina from burns and permanent scarring. Low-power binoculars won't have enough magnification to show tiny Mercury. The transit is NOT visible to the naked eye and cannot be detected through standard solar viewing glasses."

In advance of Mercury's exciting day in the spotlight, NASA released the first global topographic model of the solar system's innermost planet on Friday.